Halliday & Matthiessen (2014: 606):
However, once introduced in this way [exophorically], they [such elements] are picked up through anaphoric reference again and again, forming referential chains in the unfolding conversation: this fish – it ...; the pan – the pan – the pan – it. It is these references within the text that create cohesion of the referential kind. These references are to non-interactants. In addition, there are references to interactants, for example, Jane: mine – I. Such interactant determiners and pronouns refer outside the text to roles defined by the speech events – speaker, speaker plus others, addressee; but they can still form chains within the text, of course.
The term 'reference chain' is from Martin (1992;140) — itself derived from the original notion of an 'identity cohesive chain' (Hasan 1989/1985: 83-4).
Here Matthiessen repeats Martin's misunderstanding of reference relations as forming a chain of referents. Importantly, the reference relation holds between a reference item and its referent, not between referents. The cohesive relation between referents in the above example is lexical cohesion: the repetition of pan in the pan – the pan – the pan – it. That is, Matthiessen here repeats Martin's confusion of reference with lexical cohesion.
Cf Halliday (1985: 296; 1994: 317):